1. Technical Field
This application relates to a cutting insert having opposite plate planes of a base body with respectively one base surface for each plane, as well as at least one lateral surface. This application relates furthermore to a milling cutter with such a cutting insert. The term cutting insert is particularly to mean an indexable cutting insert and the term milling cutter is particularly to mean a milling cutter for producing or machining finished surfaces.
2. Background Information
Due to the increasing demands made of technical components or work pieces that are made by chip-forming machining, there arises particularly the demand for an improved quality of the surface finish. So as to meet this demand for smooth surfaces without furrows and grooves, and for finish-machining surfaces, particularly with a roughness (Rz) of less than 6 μm and a waviness (Wt) of less than 3 μm, there are also to be made special demands of the tools that are being used. Of particular importance herein are the geometry of the cutting edge, the selection of the cutting material, and the selection of the treatment parameters, as well as the exactly defined position of the cutting edge with respect to the surface that is being machined.
In such a milling cutter, particularly in a so-called finish-machining milling cutter, for the generation of particularly smooth surfaces, the usually used cutting inserts or indexable cutting inserts comprise essentially two opposite base surfaces that are utilized respectively as support surfaces and as clear surfaces for the main cutting edge. Four planar surfaces are arranged at the periphery, which surfaces are utilized when installed in the tool as contact surfaces and as chip surfaces for the main cutting edge that is used in the cutting contact. For the secondary cutting edge that is also in cutting contact, these planar surfaces serve respectively as secondary cutting surfaces.
Concerning the cutting edge that forms the main cutting edge, this can be linear and essentially plane-parallel with respect to the surface that is being machined. Of disadvantage are hereby the sensitivity with regard to angle errors during positioning of this linear cutting edge with respect to the work piece surface, such that a preferred approach that resides in use of only an end portion of the cutting edge at the surface that is to be machined is practically unavoidable and, accordingly, the posed requirement of an improved surface finish is practically not attainable.
As an alternative to a linear configuration and thereby a straight cutting edge, the cutting edge may comprise a circular or ellipsoidal curvature. In a cutting insert known from EP 0 370 494 B1, the curvature increases uniformly from the center of the cutting edge in the direction to the two cutting edge ends. Such a cutting edge that is circular or ellipsoidal in reference to the surface to be machined, however, due to values of curvature that are uniform or uniformly increasing commencing from the center of the cutting edge in the direction of the two cutting edge ends, entails undesirable small errors of tolerances with reference to angle errors with a cutting body radius that is increasing. In the case of a cutting edge that is configured to be circularly curved, furthermore, the diminishing of surface quality with a decrease in the radius of the cutting edge is of particular detriment.
Concerning the positioning of such a cutting insert or indexable cutting insert in the carrier system, there exist as a matter of principle two possibilities. Thus, the cutting insert or the indexable cutting insert, under unchanging positioning of the cutting edge with respect to the surface, can be fixed in the carrier or it can be connected thereto in such a way that a subsequent shifting of the position of the cutting edge, in reference to the surface that is to be machined, is possible. Of disadvantage in such position fixing of the cutting insert with an unchanging cutting edge position is the requirement of a very precise tool carrier for the cutting insert. Pursuantly, in the case of a cutting insert connection with a subsequent shift in position of the cutting edge, an increased susceptibility of the entire system with respect to shifting of the position of the cutting edge by external circumstances is of disadvantage.